Ethoxylated fatty amine surfactants are well-known adjuvants for agricultural applications. Numerous companies supply ethoxylated fatty amines, including Stepan Company (TOXIMUL® series of products), Air Products (Tomamine® products), Akzo-Nobel (Ethomeen® products), Huntsman (Surfonic® T, Teric® M, and Empilan® AM products), and others. Many of the commercial materials are ethoxylated tallow amines, where the fatty chains are principally linear and saturated C14-C18 groups. Methods for making saturated ethoxylated fatty amines are straightforward (see, e.g., U.S. Pat. No. 4,313,847) and their use in agricultural compositions, particularly glyphosate formulations, is well documented (see, e.g., U.S. Pat. Nos. 5,668,085 and 6,277,788).
Tallowamine ethoxylates have been workhorse surfactants for agricultural use, but they have some drawbacks. For instance, tallowamine ethoxylates cause an undesirable level of eye irritation, which can be a hazard during herbicide application. For at least some applications, ethoxylated etheramine surfactants (see, e.g., U.S. Pat. Nos. 5,750,468 and 8,455,396; and U.S. Publ. No. 2009/0318294) may provide a less-irritating alternative to tallowamine ethoxylates.
Tallowamine ethoxylates are also moderately toxic in aquatic invertebrate acute toxicity tests, so less-toxic alternatives are needed. Ideally, such a reduction in aquatic toxicity could be realized without sacrificing herbicidal efficacy. To address the toxicity concern, formulators often replace at least a portion of the tallowamine ethoxylate with another surfactant or additive. For instance, U.S. Publ. No. 2007/0049498 counsels to replace a portion of the tallowamine ethoxylate with glycerin to reduce the degree of aquatic toxicity and eye irritation.
Improvements in metathesis technology have led to the availability of commercial fatty acid (or ester) feedstocks having monounsaturation and reduced chain length (C10-C17), as taught in U.S. Pat. Nos. 8,569,560 and 8,481,747. The feedstocks are usually prepared by cross-metathesizing short-chain olefins with natural oils. The acid or ester feedstocks are sensible starting materials for preparing the corresponding fatty amines and ethoxylated fatty amines. Prior to the availability of metathesis-based feeds, the synthesis of monounsaturated fatty amines was usually a non-trivial, multi-step proposition (see, e.g., U.S. Pat. No. 5,236,900). However, some shorter-chain fatty acids are available by non-metathesis routes. For instance, 10-undecenoic acid, a precursor to a C11 monounsaturated amine ethoxylate, is available economically in large quantity from castor oil pyrolysis (see, e.g., U.S. Pat. No. 5,952,517).
The agricultural industry would benefit from the availability of surfactant compositions having reduced aquatic toxicity. Valuable compositions would effectively solubilize glyphosate or other important agricultural active materials and could be used in high-load formulations. Ideally, the reduced aquatic toxicity would not be achieved at the expense of herbicidal efficacy.